You are about 5 years late on this one (here is part of a conversation from 2012, detailing stuff that happened in talks in 2011,
http://gbatemp.net/threads/29c3-hacker-conference-in-a-little-under-a-week.339564/#post-4489262 ), though I suppose there is still room to grow. I will go with pure investment here as mining is a very hard game at this point.
There are plenty of people that invested and got
real more conventional money, how to then declare it for tax purposes gets tricky depending upon where you are as in many places nobody is quite sure what kind of financial instrument they are, or indeed if they are even legal in some countries.
Charts
https://bitcoincharts.com/charts/bitstampUSD#tgSzm1g10zm2g25
Had you invested in 2012 in the sub $100 range you could sell off today for north of $2200 on that exchange*. That was long ago though so had you invested in the 2014-2015 slump at somewhere under $400 you would still be able to sell for $2200 today and make a tidy profit. Had you bought in during the first 2013 high and you would have halved your money until later that year, at which point you could have sold off for some for some 4 times more. Had you bought in at the late 2013 high you would have only been able sell at a profit earlier this year. Though at the same time had you bought in during the low of early 2015 you could have made money (and the return would have been greater than most other types of investments) selling at any point from then on really. Right now there appears to be some massive growth happening (more than doubled since January) which is probably what brought it to your attention, I am not sure what is causing this one though.
*there are many exchanges out there which will sell you things and cash you out, some will even offer to store your bitcoins for you (probably before getting hacked and losing it all -- a choice phrase I once heard is there are two types of bitcoin exchange; those which have been hacked and those that don't yet know they have been hacked). Technically they can all offer different prices, and you can certainly take advantage of disparities in pricing, but most of the time they are all pretty similar, or if they are dissimilar then by the time you factor in commissions and volumes they will do in any one go/period then yeah.
There is nothing terribly special about bitcoin though and anybody can make their own. How many places take them in, and in turn how valuable they are in general, varies dramatically. Likewise the options to do some of the more interesting financial transactions with them are far more limited than conventional stocks (there are places that allow you to short bitcoin, do hedging transactions and automated selling/buying but they are not the norm).
The current hotness is probably distributed ledgers aka smart contracts, they function in a broadly similar way and can be used as currency but are aimed more at facilitating services rather than just currency exchange, one video
